The human body contains a wide variety of natural valves, such as, for example, heart valves, esophageal and stomach valves, intestinal valves, and valves within the lymphatic system. Natural valves can degenerate for a variety of reasons, such as disease, age, and the like. A malfunctioning valve fails to maintain the bodily fluid flow in a single direction with minimal pressure loss. An example of a malfunctioning valve is a heart valve that may be either stenotic, i.e., the leaflets of the valve do not open fully, or regurgitant, i.e., the leaflets of the valve do not close properly. It is desirable to restore valve function to regain the proper functioning of the organ with which the valve is associated. For example, proper valve function in the heart ensures that blood flow is maintained in a single direction through a valve with minimal pressure loss, so that blood circulation and pressure can be maintained. Similarly, proper esophageal valve function ensures that acidic gastric secretions do not irritate or permanently damage the esophageal lining.
Several percutaneous prosthetic valve systems have been described. One example described in Andersen, et. al. (U.S. Pat. No. 5,411,552) comprises an expandable stent and a collapsible valve which is mounted onto the stent prior to deployment. The collapsible valve may be a biological valve or it may be made of synthetic material. The Anderson prosthetic valve is delivered and deployed using a balloon catheter which balloon is used to expand the valve-stent prosthesis to its final size. See also, U.S. Pat. No. 6,168,614 (Andersen, et al.) entitled “Valve Prosthesis for Implantation in the Body” and U.S. Pat. No. 5,840,081 (Andersen, et al.) entitled “System and Method for Implanting Cardiac Valves.”
Spenser, et. al. (U.S. Pat. No. 6,893,460) describe another prosthetic valve device comprising a valve structure made of biological or synthetic material and a support stent. The Spenser prosthetic valve is a crimpable leafed-valve assembly consisting of a conduit having an inlet and an outlet, made of pliant material arranged to present collapsible walls at the outlet. The valve assembly is affixed to the support stent prior to deployment. The complete valve device is deployed at a target location within the body duct using a deploying means, such as a balloon catheter or a similar device.
Percutaneous implantation of prosthetic valves is safer, cheaper, and provides shorter patient recovery time than standard surgical procedures. However, current artificial percutaneous prosthetic valves have the disadvantage of being extremely bulky, even when compressed for delivery. The problem with this bulkiness is that it requires the delivery catheter to have a rather large diameter. Large catheters generally are not suitable for percutaneous procedures and require cut-down surgical procedures and/or sophisticated and difficult puncture-closure techniques. The bulkiness and large diameter of current valve devices and delivery systems combined with the anatomy through which the devices must be delivered also can make delivery into the lumen problematic from the point of view of success rate, accuracy of deployment, and risk of complications. Specifically, delivery complications may arise due to the shape of the lumen, for example, the significant natural curve of the aortic arch and/or a tortuous iliac/femoral artery through which the catheter is introduced. Further, a catheter of such diameter tends to be less flexible than a smaller diameter catheter, especially when loaded with a bulky, inflexible device. Additionally, manipulating such a loaded catheter through a narrow vessel, and in particular a curved vessel, substantially raises the potential for damage to that vessel wall, bleeding, and other vascular complications, which are in turn related to higher rates of morbidity and mortality.
Still further, the valve leaflet material makes up 80% of the percutaneous prosthetic valve delivery diameter. Current efforts to minimize the bulk of the valve leaflet material include using thinner valve material or tightly crimping the valve leaflets. Both of these procedures adversely impact the durability of the valve leaflets, the latter does so by damaging the valve material.
Therefore, a need exists to facilitate the delivery of artificial valves and also to increase the safety of the procedure. A valve device having a smaller delivery diameter than pre-assembled percutaneous valve devices and that can be delivered through a vessel without incurring further damage to the wall of the body lumen is highly desirable. It is also desirable to have a low profile (small delivery diameter) percutaneous prosthetic valve device that provides the type of leaflet durability available in surgical prosthetic valve devices.
US Published Patent Application No. 2010/0185275A1, incorporated herein by reference in its entirety, describes a modular (multi-component) percutaneous valve device that facilitates delivery of the prosthetic valve by providing the valve device as deliverable modules that may be assembled into a working configuration at or near the site of implantation in the blood vessel. US Published Patent Application No. 2010/0185275A1 also describes various means for locking together the assembled device modules.
US Published Patent Application No. 2011/0172784A1, incorporated herein by reference in its entirety, describes a modular (multi-component) percutaneous valve device having a self-assembly member that facilitates assembly of the modular prosthetic valve in the blood vessel. US Published Patent Application No. 2011/0172784A1 also describes valve modules that may assume a shape (unassembled shape) different from their functional valve shape that are particularly advantageous for delivery in that the unassembled shape permits the valve module to be folded in a manner that minimizes the delivery diameter of the device, thereby minimizing complications and increasing the safety of the valve replacement procedure.